Battery packs and electrical devices, such as power tools, are usually connected by metal terminals which are able to connect physically.
When the connection between the two metal terminals is bad, that is equivalent to a resistor with large resistance being arranged in the circuit. If a large current flows through the circuit of the two metal terminals, lots of heat is generated, so that the terminals may deform due to the heat and the connection may worsen.
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.